Regulating the spin state of a single Fe atom in BiOBr to enhance photocatalytic nitrogen reduction: insights from theoretical studies

Abstract

Herein, we investigated the effects of the spin state of a single Fe atom on the nitrogen reduction reaction (NRR) in BiOBr using density functional theory. Our simulations revealed that P doping can reduce the spin state of the single Fe atom. This leads to an overlap of orbitals between N₂ and the Fe atom at the Fermi energy level, thereby promoting the activation of N₂. The investigation of NRR mechanisms revealed that the enzymatic mechanism is more favorable compared to the distal and alternating mechanisms. The formation of NNH with an energy barrier of 2.32 eV is identified as the rate-determining step for the NRR process in the Fe-doped BiOBr system. Furthermore, P doping dramatically reduces the energy barrier of the rate-determining step, which involves releasing the second NH₃ molecule, by a factor of 2.37. This study elucidates the influence mechanism of the Fe spin state on the performance of the NRR, providing valuable theoretical guidance for designing highly efficient photocatalysts.